Quantitative Comparison of Retinal Pixel Area Imaged by Ultra-Wide Field Fundus Cameras

Abstract

Purpose : To compare the retinal pixel area imaged using the Optos P200dTx and Zeiss Clarus 500 ultra-wide field fundus cameras.

Methods : A single-center, retrospective, cross-sectional analysis of fundus photographs from eyes undergoing imaging with both the Optos P200dTx and Zeiss Clarus 500 cameras. The Optos P200dTx photos were single capture images without montage. The Zeiss Clarus 500 images were 1-3 single capture images that were montaged, when possible. The pixel areas encompassing all visible retina in four quadrants centered on the fovea were measured using Adobe Photoshop CC software. The measurements were normalized to the optic disc area for each image to account for pixel density differences. Patients and technicians were asked for their preference between the machines. Imaging session times were recorded. Pixel area and imaging time were compared using the Mann-Whitney U test. Patient and technician preference were compared using Fisher’s exact test.

Results : 82 eyes of 49 patients were included in the study. Fifteen (18.3%) of the 82 Zeiss Clarus 500 images were single capture images due to the patient being unable to take multiple images for reasons such as difficulty seeing the fixation target or comfort. The Optos P200dTx consistently imaged a larger relative pixel area in all four quadrants compared to the Ziess Clarus 500: superior: 92.4 vs. 74.9, (p <0.0001), inferior: 100.7 vs. 61.3 (p <0.0001), temporal: 145.0 vs. 91.2 (p<0.0001), and nasal: 165.2 vs. 128.3 (p <0.0001). Technicians preferred the Optos P200dTx for 28 imaging sessions, the Zeiss Clarus 500 for 20 imaging sessions, and had no preference for 1 imaging session (p=0.15). Among the 46 patients who responded, 22 preferred the Optos P200dTx, 19 preferred the Zeiss Clarus 500, and 5 had no preference (p=0.66). The average imaging session time was 4.6 minutes (SD: 3.0) for the Optos P200dTx and 5.3 minutes (SD: 3.1) for the Ziess Clarus 500 (p=0.17).

Conclusions : In the current study, the Optos P200dTx captured statistically significantly more retinal area in all four quadrants compared to the Zeiss Clarus 500. There was no statistically significant difference in patient or technician preference or image acquisition time between the two devices.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.